摘要数码相机的图像质量由三个控制模块决定：自动对焦（AF），自动曝光（AE），自动白平衡（AWB）。其中自动对焦模块是最基础的。其对于数码相机成像质量的重要性也不言而喻。本文围绕自动对焦问题进行了深入的研究和改进，主要在评价窗口自适应选择、评价指标及搜索策略这三方面进行了改进。首先，评价窗口使用了智能的选取方法。该方法综合考虑了区域的亮度、纹理和位置，依据亮度适中、纹理丰富和中心优先的准则进行对焦区域的自适应选择。其次，分析了现有的图像质量评价方法的优缺点和应用条件，并提出了一种基于评价曲线极值判断的最优评价指标的在线选择方法。再次，针对实际应用中镜头的焦距值无法获取或难以准确获取这两种情况，给出了一种新的鲁棒的盲搜索自动对焦算法。通过离线图像处理实验和在线自动对焦实验，证明本文给出或提出的方法是有效的，且能满足实时性要求。64153

毕业论文关键词  摄像机自动对焦算法研究 智能评价窗口选择  最优评价指标  盲搜索算法

毕业设计说明书（论文）外文摘要

Title    Research on auto-focus algorithm without focal   parameters                                                

Abstract Three control modules control the image quality in a digital still camera. These modules are the auto-focus(AF), auto-exposure(AE), auto-white -balance (AWB) module. The auto-focus is the most fundamental module in a digital still camera. AF algorithm performs a significant role. This dissertation is aimed at the problem of auto-focus, some analysis and improvements have been done with the process. And the improvements are mainly about the following three aspects: the selection of assessing window, the evaluating indicator , and searching strategy .Firstly, The Intelligent selection method is selected as the accessing window which combines area brightness, texture, and position together, and it chooses the focus area adaptively. Secondly, according to the analysis of merit and demerit and applied conditions of general image quality evaluation methods, an online selecting method of evaluation indicator based on extremum of appraisal curve has been applied. Thirdly, considering the fact in real applications that the focus-value can't be obtained or obtained accurately, a new robust blind searching auto-focus algorithm is given. Both offline image processing and online auto-focusing experiments contribute the effectiveness of the methods this dissertation has come up with, and also can qualify for the real-time application.

Keywords  Camera Auto-Focus Algorithm Research Intelligent Selection of Assessing Windows  Best Evaluating Indicator   Blind Search Algorithm

目录

1 绪论 5

1.1  问题的提出和意义 5

1.2  国内外研究现状 5

1.3  本文的主要研究内容和结构安排 7

2 摄像机自动对焦原理简介 8

2.1  自动对焦系统框架图 8

2.2  对焦原理简介 8

3 摄像机自动对焦评价窗口选取 9

3.1  设定图像评价窗口意义 9

3.2  常用图像评价窗口选取方法